U.S. patent application number 13/632440 was filed with the patent office on 2013-04-04 for method for pressure-independent, refillable drug infusion device.
This patent application is currently assigned to ANIMAS CORPORATION. The applicant listed for this patent is Luis G. Jahn, Sean M. O'Connor. Invention is credited to Luis G. Jahn, Sean M. O'Connor.
Application Number | 20130085470 13/632440 |
Document ID | / |
Family ID | 47993294 |
Filed Date | 2013-04-04 |
United States Patent
Application |
20130085470 |
Kind Code |
A1 |
O'Connor; Sean M. ; et
al. |
April 4, 2013 |
METHOD FOR PRESSURE-INDEPENDENT, REFILLABLE DRUG INFUSION
DEVICE
Abstract
Described is drug infusion device with one or more check valves
for inhibiting the unintentional discharge of medication from a
cartridge. The device includes a chamber capable of receiving a
cartridge of medication in a fluid form and one or more novel check
valves for ensuring the drug is not unintentionally released due to
pressure differentials between the cartridge and the ambient
pressure outside of the drug infusion device.
Inventors: |
O'Connor; Sean M.; (West
Chester, PA) ; Jahn; Luis G.; (Royersford,
PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
O'Connor; Sean M.
Jahn; Luis G. |
West Chester
Royersford |
PA
PA |
US
US |
|
|
Assignee: |
ANIMAS CORPORATION
West Chester
PA
|
Family ID: |
47993294 |
Appl. No.: |
13/632440 |
Filed: |
October 1, 2012 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61540595 |
Sep 29, 2011 |
|
|
|
Current U.S.
Class: |
604/500 |
Current CPC
Class: |
A61M 5/16881 20130101;
A61M 5/1452 20130101; A61M 2039/246 20130101; A61M 2039/242
20130101 |
Class at
Publication: |
604/500 |
International
Class: |
A61M 5/168 20060101
A61M005/168 |
Claims
1. A method, comprising: providing a drug infusion device having a
reservoir and at least two check valves, wherein at least one of
the check valves comprises a pre-biased disc spring element;
creating a pressure within the reservoir that is greater than the
cracking pressure of the pre-biased disc spring element; and
expelling fluid from the reservoir through an outlet channel.
2. The method of claim 1 wherein at least one of the check valves
comprises a flap valve comprising a compliant material and is in a
closed position when a positive pressure exists within the
reservoir.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application relates to U.S. patent application Ser. No.
61/540,595, filed Sep. 29, 2011; all applications are herein
incorporated by reference in their entireties.
FIELD OF THE INVENTION
[0002] The present invention relates, in general, to drug delivery
devices and, more particularly, to a method for avoiding excess
pressure differentials in portable drug infusion devices, to
inhibit the unintentional discharge of drug due to pressure changes
and/or siphoning.
BACKGROUND OF THE INVENTION
[0003] The use of drug delivery devices for various types of drug
therapy is becoming more common as the automated infusion of a drug
may provide more reliable and more precise treatment to a
patient.
[0004] Diabetes is a major health concern, as it can significantly
impede on the freedom of action and lifestyle of persons afflicted
with this disease. Typically, treatment of the more severe form of
the condition, Type I (insulin-dependent) diabetes, requires one or
more insulin injections per day, referred to as multiple daily
injections. Insulin is required to control glucose or sugar in the
blood, thereby preventing hyperglycemia that, if left uncorrected,
can lead to ketosis. Additionally, improper administration of
insulin therapy can result in hypoglycemic episodes, which can
cause coma and death. Hyperglycemia in diabetics has been
correlated with several long-term effects of diabetes, such as
heart disease, atherosclerosis, blindness, stroke, hypertension,
and kidney failure.
[0005] The value of frequent monitoring of blood glucose as a means
to avoid or at least minimize the complications of Type I diabetes
is well established. Patients with Type II (non-insulin-dependent)
diabetes can also benefit from blood glucose monitoring in the
control of their condition by way of diet and exercise. Thus,
careful monitoring of blood glucose levels and the ability to
accurately and conveniently infuse insulin into the body in a
timely manner is a critical component in diabetes care and
treatment.
[0006] To more effectively control diabetes in a manner that
reduces the limitations imposed by this disease on the lifestyle of
the affected person, various devices for facilitating blood glucose
(BG) monitoring have been introduced. Typically, such devices, or
meters, permit the patient to quickly, and with a minimal amount of
physical discomfort, obtain a sample of their blood or interstitial
fluid that is then analyzed by the meter. In most cases, the meter
has a display screen that shows the BG reading for the patient. The
patient may then dose theirselves with the appropriate amount, or
bolus, of insulin. For many diabetics, this results in having to
receive multiple daily injections of insulin. In many cases, these
injections are self-administered.
[0007] Due to the debilitating effects that abnormal BG levels can
have on patients, i.e., hyperglycemia, persons experiencing certain
symptoms of diabetes may not be in a situation where they can
safely and accurately self-administer a bolus of insulin. Moreover,
persons with active lifestyles find it extremely inconvenient and
imposing to have to use multiple daily injections of insulin to
control their blood sugar levels, as this may interfere or prohibit
their ability to engage in certain activities. For others with
diabetes, multiple daily injections may simply not be the most
effective means for controlling their BG levels. Thus, to further
improve both accuracy and convenience for the patient, insulin
infusion pumps have been developed.
[0008] Insulin pumps are generally devices that are worn on the
patient's body, either above or below their clothing. Because the
pumps are worn on the patient's body, a small and unobtrusive
device is desirable. Some devices are waterproof, to allow the
patient to be less inhibited in their daily activities by having to
remove their drug infusion device while showering, bathing, or
engaging in various activities that might subject their infusion
device to moister, such as swimming. In such devices, it would be
desirable to have a structure and method for verifying proper
function of venting system within the device, since vents are
typically passive devices that have no means for self-diagnostic
checks to verify function has been compromised (i.e. intentional or
unintentional obstruction of vent opening(s)). Further, it would be
desirable to be able to alert the user of abnormal pressure
differentials within their device that may cause erratic or
unintentional drug delivery. Finally, it would be desirable for a
drug infusion device to incorporate means for detecting the
altitude at which the device is located, to avoid problems
associated with air travel and sporting activities such as mountain
climbing, skydiving, etc. that patients may wish to engage in
without having to forego the use of their drug infusion device for
concerns over erratic or unintentional drug delivery due to rapid
pressure changes in and around the device.
[0009] Further, it would be desirable for a portable infusion pump
to have means to inhibit the unintended discharge of drug caused by
pressure differentials and siphoning, as it has been a longstanding
problem in the art that these phenomena may occur when the pressure
outside of a drug-containing reservoir decreases below the pressure
inside of the reservoir. This problem is particularly notable for
insulin-dependent diabetic who must disconnect and remove their
portable insulin pumps during air travel to avoid accidental and
potentially harmful overdosing of medication.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The novel features of the invention are set forth with
particularity in the appended claims. A better understanding of the
features and advantages of the present invention will be obtained
by reference to the following detailed description that sets forth
illustrative embodiments, in which the principles of the invention
are utilized, and the accompanying drawings of which:
[0011] FIG. 1 illustrates an exemplary embodiment of a drug
infusion device according to the present invention, in
cross-section.
[0012] FIG. 2 illustrates another exemplary embodiment of a drug
infusion device according to the present invention in exploded
view.
[0013] FIG. 3 illustrates another exemplary embodiment of a drug
infusion device according to the present invention in perspective
view and partly in cross-section.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS OF THE
INVENTION
[0014] In an exemplary embodiment, the invention is directed to
structures and methods for avoiding the accidental or unintentional
discharge of medication from a portable drug infusion device caused
by pressure differentials between the compartment that houses the
drug reservoir of a portable drug infusion pump and the external
environment (atmosphere).
[0015] Some portable infusion pumps are designed to be waterproof.
This is an attractive feature for people with active lifestyles who
benefit from continuous drug infusion (i.e. infusion of insulin for
people with diabetes). Such devices must be designed with sealed
enclosures/housings to prevent ingress of water. To avoid the
development of pressure differentials between the external
environment and the sealed compartment that houses the drug
reservoir, most waterproof pumps incorporate hydrophobic vents that
allow passage of air, but not fluids (within certain limitations of
pressure differential).
[0016] Most portable drug infusion pump reservoirs are similar in
design to that of a standard syringe. Therefore, the reservoir is
typically comprised of two major components; a cylindrical barrel,
with a connector integrated into the distal end for attachment of
an infusion line set, and a movable plunger with an elastomer seal.
The plunger is inserted into the open proximal end of the barrel to
form a closed volume. To deliver drug, a mechanically driven piston
is advanced forward, which in turn advances the cartridge plunger
forward, reducing the internal volume of the cartridge, thus
displacing fluid. Typically, the piston (part of the durable
device) is not mechanically interlocked with the cartridge plunger
because there is no need to retract the plunger once the cartridge
has been filled and subsequently installed in the pump.
[0017] Because the pump piston is not interlocked with the
cartridge plunger, there is a risk of unintentional delivery of
drug if a positive pressure differential were to develop between
the chamber that houses the reservoir and the external environment
(location of infusion site). A positive pressure differential would
impart a resultant force on the plunger which is directly
proportional to the cross-sectional area of the drug reservoir's
internal volume. If the resultant force exceeds the sustaining
force of the cartridge plunger it will advance the plunger forward
and thus deliver drug.
[0018] In one embodiment, the disclosed invention is a portable
drug infusion pump with a mechanism for inhibiting the discharge of
fluid from the pump's drug reservoir when the chamber containing
the reservoir experiences a high pressure than the ambient
environment. Most commonly this occurs in situations where the
device is moved to locations where the atmospheric pressure is low,
such as in an airplane, and drug is forced from the reservoir due
to the pressure differential, e.g., the reservoir is at a higher
pressure than ambient, thus causing the unintentional flow of drug
out of the reservoir.
[0019] In an exemplary embodiment, the invention includes a drug
reservoir with check valve. Typically, the reservoir is a
syringe-like rigid cartridge for use in a portable drug infusion
pump. The advantage of this novel design is that it prevents
unintentional delivery of drug due to atmospheric pressure
differentials or head height pressure differentials (i.e.
siphoning). The check valve is in fluidic outlet path and requires
a minimum positive pressure differential (cracking pressure) to
open and allow flow of drug from the reservoir. The geometry of the
check valve components determines the cracking pressure and can be
adjusted to meet the functional requirements of the device in which
it is to be used.
[0020] The device will typically include a housing containing a
chamber. The chamber is configured to receive a cartridge
containing a quantity of fluid. The fluid is typically a drug
formulation, but on occasion may comprise saline or other material.
At the interface between the chamber and the inserterd cartridge is
a preferred location for a check valve. The check valve may be
constructed of a metal spring element in the shape of a disc. The
geometry cut into the disc creates spring arms and a central
surface that functions as a valve poppet. The valve seat may be
constructed of an elastomer. The check valve described is the
preferred embodiment, but the main elements of the check valve can
be constructed in many configurations that produce the same
functional results. For example, the elastomer valve seat could
instead be constructed of a rigid material, and an elastomer disc
could either be mechanically attached to the center of the metal
spring element, or overmolded onto the metal spring element.
[0021] The check valve is installed inside the cartridge barrel at
the bottom surface of the main bore and defines the interior volume
of the reservoir. The check valve can be attached via a mechanical
interference fit, ultrasonic weld, adhesive, or other standard
methods of attachment typically used in disposable medical
devices.
[0022] The check valve could be constructed of (5) components:
[0023] 1) Substrate: Substrate would be an injection molded
component made of a rigid polymer. Rigid polymer Substrate would
support and orient check valve seat and support the perimeter one
way valve. Rigid polymer Substrate would also define fluidic paths
for both valves. Rigid polymer Substrate could also incorporate
energy director geometries for attachment of check valve assembly
to cartridge barrel of drug reservoir.
[0024] 2) Check Valve Seat: An elastomer structure that could be
overmolded onto the rigid polymer Substrate, or attached to the
rigid polymer Substrate. The compliant elastomer structure
functions as a check valve and works in conjunction with the Spring
Element Disc.
[0025] 3) Spring Element Disc: Spring Element Disc is a thin metal
component of circular shape with geometry cut into it to form
spring arms and a central poppet surface. Spring Element Disc could
be photo-etched in a batch or continuous feed process to produce a
precision geometry at minimal cost.
[0026] 4) One Way Valve Flap: An elastomer structure that could
also be overmolded onto the rigid polymer Substrate, or attached to
the rigid polymer Substrate. The compliant elastomer structure
would function as a one way valve in conjunction with mating
surfaces of the Cartridge Barrel.
[0027] 5) Cartridge Barrel: Bottom of Cartridge Barrel bore
incorporates geometry that accepts and aligns the Spring Element
Disc, and subsequently the overmolded Substrate (with overmolded or
attached Check Valve Seat and One Way Valve Flap). The Substrate
can then be attached (e.g. ultrasonically welded) to the Cartridge
Barrel, trapping the Spring Element Disc between the Substrate and
Cartridge Barrel. The Cartridge Barrel would also incorporate
geometry at the bottom of its bore to act as a seat for the one way
valve. Once assembled, both check valve and one way valve function
are established.
[0028] Embodiments of the present invention allow end user to fill
cartridge with drug in the same manner that a syringe would be
filled. This is accomplished with a second one way-valve that is
incorporated into the supporting structure of the check valve. When
the plunger of the syringe-like cartridge is retracted, a negative
pressure is created within the reservoir volume. This causes the
one-way valve to open and allow drug to transfer from the vial to
the reservoir. When the plunger is advanced forward the one-way
valve closes and a positive pressure develops which is proportional
to the force applied to the plunger. Once the internal positive
pressure within the reservoir exceeds the cracking pressure of the
check valve, the check valve opens and drug is dispensed. Typically
this retracting and advancing motion is repeated several times
during filling until all visible air is purged from the cartridge
reservoir and the desired amount is transferred.
[0029] Check valve assembly disclosed is not limited to
installation in the cartridge reservoir. It could be installed
anywhere in the fluidic path between the drug reservoir and
infusion site. Other viable locations for the check valve assembly
are the proximal connector of the infusion line, the distal end of
the infusion line, or anywhere in between. The check valve assembly
could also be built into an independent adapter that could be
placed between the cartridge reservoir and the infusion line.
[0030] Turning to the specific features shown in the drawings
figures, FIG. 1 illustrates an embodiment of the present invention.
The drug delivery device 100 includes a drug reservoir 111 and
check valve shown in its component parts. The check valve may
comprise a valve body 135 that rests against the substrate 150 and
a disc spring 130. The substrate may be secured to the luer 121 via
a weld joint 151 that is created by, for example, an ultrasonic
weld. The weld joint 151 may secure the substrate 150 to the luer
by a variety of other manufacturing methods.
[0031] During drug delivery, an increase in pressure within the
reservoir 111 biases the fluid from the reservoir against the
poppet 131 of the disc spring 130. If sufficient pressure is used,
also known as the cracking pressure, the spring arms 132 of the
disc spring 130 will permit movement of the poppet 131 to allow
fluid to pass from the reservoir 111 through outlet channel 161 and
then delivered from the device 100 via the external fluid path 120,
120' of the luer 121.
[0032] When there is no pressure biasing fluid out of the reservoir
111, the poppet 131 rests against the valve seat 162 with a bias
provided by the spring arm 132 and a seal created by a compliant
material that creates a dynamic seal 163. The valve body 135 may
include a contact surface 152 as a point to transfer energy for
welding and a dynamic outlet seal structure 160 which may be
comprised of a compliant material. The periphery of the valve body
135 may also be configured with an inlet flap valve 164 to form the
dynamic inlet seal 165 to inhibit the unintended ingress of fluid
via inlet channel 153.
[0033] The disc spring 130 may be disposed within the luer 121 and
configured to rest on a static seal structure 140 that is
preferably made of a compliant or similar material to ensure
against leakage of gas or fluid into or out of the reservoir. The
static seal structure may include a static seal ridge 142 to
provide a convenient site for bonding, welding, fusing, or
otherwise attaching the static seal structure 140 to the luer 121.
Further, the static seal structure 140 may include a protusion or
other suitable surface to form a disc spring support 141.
[0034] FIG. 2 illustrates an embodiment of the check valve of the
present invention. Shown is the cartridge barrel 110 having a
static seal structure 140 and a static seal ridge 142. A disc
spring 130 is configured to be disposed on the disc spring support
(not shown) and includes a poppet 131 that is moveably attached to
the disc spring 130 by a spring arm 132. One or more spring arms
132 or equivalent structure may be used to permit biased movement
of the poppet 131 to and away from the disc spring 130.
[0035] Illustratively, a compliant dynamic seal structure 160
having a valve seat 162 for contacting the poppet 131 is configured
to mate with the cartridge barrel 110. The dynamic seal structure
160 may, on one side, have one or more contact surfaces 152 that
may provide a site for welding during manufacturing and, on another
side, include rigid substrate 150 in which the inlet channel 153 is
formed. An outlet channel 161 can also be formed in the dynamic
seal structure 160. The periphery of the dynamic seal structure 160
may also include an inlet valve flap 164 to ensure uniform contact
between the dynamic seal structure of the valve 135 and the
cartridge barrel 110.
[0036] FIG. 3 further illustrates an embodiment of the valve 135 of
the invention in which the substrate 150 is shown having the outlet
channel 161 formed in its center and extending through a valve seat
162. Formed in the substrate 150 is also an inlet channel 153. One
surface of the substrate 150 may include a disc spring support 141
and a weld joint 151.
[0037] The method of delivering drug from a device in accordance
with the illustrative embodiments of the present invention follows.
Exemplary of the method is to provide a device having a cartridge
barrel with a reservoir for holding medication, such as those shown
in FIGS. 1-3. When the reservoir 111 of the cartridge barrel 110 is
filled with a fluid (typically a therapeutic agent or drug of some
type), it is important to minimize or eliminate the ability of
fluid to be accidentally expelled from the reservoir 111 through
the outlet channel 161 and spilled or delivered into a patient via
the external fluid path 120, 120'. When there is a jarring,
shaking, or other event that can force expulsion of fluid, or when
the pressure outside of the system decreased (such as during
airline travel), the flap valve 164 is biased by the pressure
differential against the housing of the cartridge barrel 110 to
create the dynamic seal 165.
[0038] Fluid, however, is not able to exit the system due unless
the cracking pressure against the valve poppet 131 is sufficient to
overcome the spring bias of the spring arm (or arms) 132 of the
disc spring 130. Mounting the disc spring 130 in the manner shown
in FIG. 1 results in the poppet being displaced relative to the
plane of the perimeter of the disc spring 130 because the spring
arm(s) 132 are in a pre-biased attitude. For this reason, enough
pressure must be exerted against the poppet 131 to overcome the
negative bias of the spring arm(s) 132.
[0039] When in use, however, the drug delivery device herein
described can employ a drive system that creates sufficient
pressure within the reservoir to exert enough hydraulic pressure
against the valve poppet 131 to overcome the negative bias of the
spring arm(s) 132. This permits the passage of fluid through outlet
channel 160 which may then exit the system via the external fluid
path 120.
[0040] In order to refill the reservoir, fluid is injected via the
external fluid path 120. The pressure of this fluid against the
valve poppet 130 increases the negative bias that strengthens the
seal between the valve poppet 130 and the valve seat 162 upon which
it rests. Fluid may, however pursue the path of least resistance
and enter inlet channel(s) 153 creating a bias against the flap
valve 164. If the flap valve 164 comprises a compliant (or
flexible) material, very little pressure is required to overcome
the cracking pressure of the dynamic seal 165, allowing fluid to
enter the reservoir, thereby refilling the device without the need
for alternative fluid paths designed specifically for that task
that might increase production costs or the complexity of the
device and, further, minimize the possibility of contamination in
the reservoir or unintended fluid expulsion.
[0041] It will be recognized that equivalent structures may be
substituted for the structures illustrated and described herein and
that the described embodiment of the invention is not the only
structure, which may be employed to implement the claimed
invention. In addition, it should be understood that every
structure described above has a function and such structure can be
referred to as a means for performing that function. While
embodiments of the present invention have been shown and described
herein, it will be obvious to those skilled in the art that such
embodiments are provided by way of example only. Numerous
variations, changes, and substitutions will now occur to those
skilled in the art without departing from the invention.
[0042] It should be understood that various alternatives to the
embodiments of the invention described herein may be employed in
practicing the invention. It is intended that the following claims
define the scope of the invention and that methods and structures
within the scope of these claims and their equivalents be covered
thereby.
* * * * *